Multi-vane centrifugal fan

ABSTRACT

A multi-vane centrifugal fan has a fan housing and an impeller. The impeller includes a plurality of vanes arranged with a prescribed spacing in the circumferential direction and fixed to a hub rotatably driven around a shaft core. The impeller further includes an annular member for reinforcement that is provided on a side of the vanes opposite the hub. The fan housing has a bell mouth with a recessed part that is provided around a circumference of an air suction port of the fan housing. The recessed part has air suction port side end parts positioned on the side of the vanes opposite the hub and rotatably inserted in the recessed part without having a shroud.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. National stage application claims priority under 35 U.S.C.§119(a) to Japanese Patent Application Nos. 2003-126122, filed in Japanon May 1, 2003, and 2004-125427, filed in Japan on Apr. 21, 2004, theentire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention of the present application relates to the structure of amulti-vane centrifugal fan.

RELATED ART

Among multi-vane centrifugal fans, there is one as depicted in FIG. 7through FIG. 9, for example. This multi-vane centrifugal fan comprisesan impeller 103 and a fan housing 104.

The impeller 103 comprises a hub 131, numerous vanes 133, 133, . . . andan annular member 132. With the impeller 103, one end 133 c of thenumerous vanes 133, 133, . . . are fixed to the hub 131 capable ofrotating about a shaft core, and are provided and arranged spaced apartby a predetermined spacing in the circumferential direction. Inaddition, with the impeller 103, the annular member 132, which is forreinforcement, is mated and fixed to the outer circumference of the endparts 133 d on the opposite side of the numerous vanes 133, 133, . . .This impeller 103 is housed inside the fan housing 104.

An air suction port 105 is formed in the fan housing 104, surrounded bya curved part 105 a that is arcuate in the air suction direction, asdepicted in FIG. 7. In addition, the fan housing 104 has a scrollstructure having an air blow out port 141 in the centrifugal direction.The impeller 103 is housed and supported inside this fan housing 104 viaa motor shaft 102 a of an impeller drive motor 102. When the motor shaft102 a is rotatably driven by the impeller drive motor 102, the airsucked in from the air suction port 105 is blown out into a vortexchamber 140 in the fan housing 104 via vane passageways between thevanes 133, 133, . . . , and the air is subsequently blown out from theair blow out port 141 to the outside, as depicted by the arrows of thevirtual lines (the chain double-dashed line) in FIG. 7.

The abovementioned type of multi-vane centrifugal fan comprises anannular bell mouth that includes the curved part 105 a formed around thecircumference of the air suction port 105 of the fan housing 104, butthe impeller 103 has a shroudless structure that does not comprise amember (a so-called shroud) having a surface opposing this bell mouth. Asirocco fan having such a shroudless structure is disclosed in JapaneseUnexamined Utility Model Application Publication No. S59-182698 (pp.2-6, FIG. 1 through FIG. 5).

If such a shroudless structure is adopted, then it is possible to reducethe number of parts in proportion to the absence of a shroud and tothereby reduce the weight of the multi-vane centrifugal fan, comparedwith the case wherein a structure having a shroud is adopted, asdisclosed in Japanese Examined Published Patent Application No.H07-27097.

SUMMARY OF THE INVENTION

In the case of the multi-vane centrifugal fan having a shroudlessstructure, a vane width W1 of the vane 133 is fixed from an air inletside edge part 133 a (the portion on the shaft core side) to an airoutlet side edge part 133 b (the portion on the side opposite the shaftcore), as depicted in FIG. 9, for example. In addition, the shape of theend part 133 d on the air suction port 105 side is also flat, the sameas the portion on the hub 131 side. Accordingly, the sealing performanceis low in the vicinity of the air suction port 105. Consequently, asdepicted in FIG. 7, for example, a reverse flow region R is generated inthe vicinity of the end part 133 d (refer to FIG. 9) on the air suctionport 105 side of the air outlet side edge part 133 b of the vane 133,and there is consequently a problem of increased aerodynamic noisebecause of the increased relative velocity of the blown out air flow inthe vicinity of the air outlet side edge part 133 b of the vane 133.

In addition, turbulence due to interference is generated in the gapbetween the inner surface of the arcuate curved part 105 a of the airsuction port 105 and the impeller 103. This is also a source ofaerodynamic noise.

Aspects of the present invention solve such problems, with a shroudlessmulti-vane centrifugal fan as discussed above, wherein the bell mouthhaving a recessed part of a prescribed depth is provided around thecircumference of the air suction port, and the air suction port side endpart of each vane is sealably shaped corresponding to the crosssectional shape of the recessed part of the bell mouth. Thereby, amulti-vane centrifugal fan is provided that reliably solves the problemsdiscussed above, and reduces running noise as much as possible.

A multi-vane centrifugal fan according to one aspect of the presentinvention comprises an impeller, and a fan housing. The impellercomprises a hub, numerous vanes, and an annular member forreinforcement. The hub is rotatably driven around a shaft core. Thenumerous vanes are provided and arranged with a prescribed spacing inthe circumferential direction of the hub, and are fixed to the hub. Theannular member is provided on the side of the numerous vanes oppositethe hub. The fan housing rotatably houses the impeller therein. Inaddition, an air suction port is formed in the fan housing. Furthermore,a bell mouth having a recessed part of a prescribed depth is provided inthe fan housing around the circumference of the air suction port.Further, air suction port side end parts (portions positioned on theside opposite the hub) of the numerous vanes are rotatably insertedinside the recessed part of the bell mouth, without having a shroud.

Here, sealing performance increases because a bell mouth having arecessed part is provided, and the air suction port side end part ofeach vane is inserted into the recessed part of the bell mouth. Namely,a reverse flow of air is suppressed in the vicinity of the air suctionport side end part of the air outlet side portion of the vane, and theflow speed distribution becomes nearly uniform over the entire area onthe air outlet side of the impeller. Thereby, aerodynamic noise isreduced.

In addition, if the gap between the bell mouth and the air suction portside end part of each vane is reduced, interference decreases, and theresulting aerodynamic noise also decreases.

In addition, if the gap between the bell mouth and the air suction portside end part of each vane is reduced, it is preferable to make theshape of the air suction port side end part of each vane a sealableshape that corresponds to the cross sectional shape of the recessed partof the bell mouth.

In addition, assuming a vane, for example, with a conventionalconstitution having a fixed vane width, if the portion inserted in therecessed part of the bell mouth is formed in the vane by cutting out apart of the air suction port side end part of that vane, then the weightof the vane decreases by just that portion, the load on the motordecreases, and the breaking strength of the vane increases.

In addition, it is preferable to make the vane width, which is thelength of the numerous vanes in the shaft core direction, so that theair outlet side is made smaller than the air inlet side, and so that itdecreases with a prescribed variation pattern from the air inlet side tothe air outlet side. In so doing, a more favorable sealing performancecan be achieved in the vicinity of the bell mouth.

In addition, the prescribed variation pattern wherein the vane width isreduced from the air inlet side to the air outlet side is preferably: apattern wherein the shape of the air suction port side end part variesin a curved shape from the air inlet side to the air outlet side; apattern wherein the shape of the air suction port side end part variesin an arcuate shape having a prescribed curvature from the air inletside to the air outlet side; or a linear variation pattern wherein theshape of the air suction port side end part varies linearly from the airinlet side to the air outlet side.

By adopting such a variation pattern, the air sucked in from the airsuction port can be blown out more smoothly in the centrifugal directionbecause the vane width of the air outlet side portion is reduced whilemaking the vane width of the air inlet side portion of each vane large.

In addition, it is preferable to provide the annular member positionedat the portion that is the air outlet side of the numerous vanes wherethe vane width that is the length of the numerous vanes in the shaftcore direction is smallest, and that is the air suction port side.According to such a constitution, if the air suction port is disposedtoward the upper side, the center of gravity of the impeller shiftsdownward, and the rotational state thereof becomes more stable.

A multi-vane centrifugal fan according to another aspect of the presentinvention comprises an impeller and a fan housing. The impellercomprises a hub, numerous vanes, and an annular member forreinforcement. The hub is rotatably driven around a shaft core. Thenumerous vanes are provided and arranged with a prescribed spacing inthe circumferential direction of the hub, and are fixed to the hub. Theannular member is disposed on the outer side in the radial direction ofthe numerous vanes, and is integrated with the end parts on the side ofthe numerous vanes opposite the hub. The fan housing rotatably housesthe impeller therein. The spaces interposed between adjacent vanes ofthe impeller are fully open in the shaft core direction and in thedirection of the side opposite the hub. The air suction port is formedin the fan housing, and a bell mouth having a recessed part of aprescribed depth is provided in the fan housing around the circumferenceof the air suction port. Further, air suction port side end partspositioned on the side of the numerous vanes opposite the hub areinserted inside the recessed part of the bell mouth.

Here, sealing performance increases because a bell mouth having arecessed part is provided, and the air suction port side end part ofeach vane is inserted into the recessed part of the bell mouth. Namely,a reverse flow of air is suppressed in the vicinity of the air suctionport side end part of the air outlet side portion of the vane, and theflow speed distribution becomes nearly uniform over the entire area onthe air outlet side of the impeller. Thereby, aerodynamic noise isreduced.

In addition, because the annular member is disposed on the outer side ofthe vanes in the radial direction, and because the spaces interposed byadjacent vanes are completely open in the shaft core direction and inthe direction of the side opposite the hub, the annular member and thevanes can be easily formed by integral molding.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a horizontal cross sectional view that depicts theconstitution of a multi-vane centrifugal fan according to the firstembodiment of the invention of the present application.

FIG. 2 is a longitudinal cross sectional view that depicts theconstitution of the multi-vane centrifugal fan.

FIG. 3 is an oblique view that depicts the constitution of an impellerof the multi-vane centrifugal fan.

FIG. 4 is a front view that depicts the constitution for all of thevanes of the impeller.

FIG. 5 is a front view that depicts the constitution for all of thevanes of the impeller according to the second embodiment.

FIG. 6 is a front view that depicts the constitution for all of thevanes of the impeller according to the third embodiment.

FIG. 7 is a cross sectional view that depicts the constitution of aconventional multi-vane centrifugal fan.

FIG. 8 is an oblique view that depicts the constitution of an impellerof a conventional multi-vane centrifugal fan.

FIG. 9 is a front view that depicts the constitution of all of the vanesof the impeller of a conventional multi-vane centrifugal fan.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 1 through FIG. 3 depict the constitution of the multi-vanecentrifugal fan according to the first embodiment of the invention ofthe present application. This multi-vane centrifugal fan 1 comprises animpeller drive motor 2, an impeller 3, and a fan housing 4, as depictedin FIG. 1 and FIG. 2. The impeller 3 is supported by a rotary shaft 2 aof the impeller drive motor 2, and is rotatably driven by the impellerdrive motor 2. The fan housing 4 rotatably houses the impeller 3 via therotary shaft 2 a of the impeller drive motor 2. This fan housing 4comprises an air suction port forming plate 6, a bell mouth 7, and thelike. The air suction port forming plate 6 forms an air suction port 5.The air suction port 5 is positioned concentric with a rotational axisO-O (shaft core) of the impeller 3, and has a size corresponding to theinner diameter of the impeller 3. The bell mouth 7 is positioned aroundthe circumference of the air suction port 5.

The impeller 3 comprises a hub 31, numerous vanes 33, 33, . . . , and anannular member 32 for reinforcement. The disc shaped hub (main plate) 31is rotatable about the rotational axis O-O. Each of the numerous vanes33, 33, . . . has a prescribed vane width/vane outer diameter ratio. Thenumerous vanes 33, 33, . . . are each fixed to the hub 31 and providedand arranged in the circumferential direction with a prescribed vanespacing and at a prescribed vane angle corresponding to the rotationaldirection of the hub 31. The annular member 32, which is forreinforcement, is mated and fixed to, or integrally formed with, theouter circumferential portion of each of the vanes 33 on the sideopposite the hub 31 (the air suction port 5 side). Furthermore, theannular member 32 is disposed on the outer side in the radial directionof the numerous vanes 33, 33, . . . .

Furthermore, in the case of the impeller 3 of the first embodiment, anend part 33 c of each of the vanes 33, 33, . . . on the hub 31 side isflat, and is provided and arranged in an orthogonal state and fixed tothe surface of the hub 31. However, an air suction port side end part(end part on the air suction port 5 side) 33 d of each of the vanes 33,33, . . . on the side opposite the hub 31 is curved. As depicted indetail in FIG. 4, the vane width of an air inlet side edge part (endpart on the rotational axis O-O side) 33 a of each of the vanes 33, 33,. . . is the vane width W1, which is identical to the vane width of thevane of the conventional impeller discussed earlier (refer to FIG. 9).In contrast, the air outlet side edge part (end part on the sideopposite the rotational axis O-O) 33 b of each of the vanes 33, 33, . .. has a vane width W2 smaller than the vane width W1 by just aprescribed dimension W3. Furthermore, the air outlet side (the sideopposite the rotational axis O-O side) is notched so that the shape ofthe end of each of the vanes 33, 33, . . . forms an arcuate shape of aprescribed curvature that is inwardly recessed. Thus, each of the vanes33, 33, . . . is constituted so that the vane width becomes smaller inan arcuate pattern of a prescribed curvature from the air inlet sideedge part 33 a to the air outlet side edge part 33 b.

As will be discussed later, this arcuate shape is formed correspondingto the cross sectional shape of a recessed part 7 a, having a prescribeddepth, of the bell mouth 7 provided around the circumference of the airsuction port 5. In a state wherein the air suction port side end part 33d of each of the vanes 33, 33, . . . is loosely fitted inside therecessed part 7 a as depicted in FIG. 2, any one of a front edge facepart A, a tip face part B, or an arcuate end face part C of each airsuction port side end part 33 d has a spacing (clearance) to the innercircumferential surface of the recessed part 7 a of the bell mouth 7that is smaller than other portions. Thereby, the generation of thereverse flow region R as discussed earlier is suppressed, interferenceand leakage flow generated due to the presence of a gap between the airsuction port side end part 33 d of the vane 33 and the innercircumferential surface of the recessed part 7 a of the bell mouth 7 aresuppressed, thereby suppressing turbulence due to that leakage flow andinterference, and achieving a reduction in ventilation noise.

The annular member 32, which is for reinforcement, is mated and fixed tothe portion that is the air suction port side end part 33 d of each ofthe vanes 33, 33, . . . and that are the air outlet side edge parts 33b, 33 b, . . . , and is integrated with the vanes 33, 33, . . . each ofthe air outlet side edge parts 33 b, 33 b, . . . is the portion of theminimum vane width W2, as shown in FIG. 4.

As depicted in FIG. 1, the fan housing 4 forms an overall scrollstructure, and its cross section forms a continuous plurality of arcseach having differing radii. The passageway that forms an air blow outport 41 of the fan housing 4 is shaped extending from an arcuate surfacepositioned on the most downstream side of the scroll portion andtangential to a prescribed air blow out direction, and its radii aresubstantially equal.

A recessed part 7 a is formed in the bell mouth 7. The recessed part 7a, having a prescribed depth, has a cross sectional shape suitable forthe air suction port side end part (tip portion extending from theannular member 32) 33 d of each of the tapered vanes 33, 33, . . . , asdepicted in FIG. 4., to loosely fit rotatably with a small clearance ona level so that a leakage flow is not generated. Specifically, therecessed part 7 a protrudes upward (in the air flow upstream sidedirection) from the air suction port forming plate 6, as depicted inFIG. 2. The extent of the protrusion corresponds to the width W3 of thetapered portion of the air suction port side end parts 33 d, 33 d, . . .of the vanes 33, 33, . . . . The shape of the tapered portions of theair suction port side end parts 33 d, 33 d, . . . having a width W3 andthe shape of the recessed part 7 a are related, as depicted in FIG. 2.

The mutually continuous portion (the boundary portion) between the airsuction port forming plate 6 and the bell mouth 7 is provided with astep part 6 a, as depicted in FIG. 2, whose width (the step) correspondsto the width (the thickness) of the annular member 32. Thereby, the vanewidth W2 portion from the annular member 32 to the hub 31 corresponds tothe widths of the passageways of a vortex chamber 40 and the air blowout port 41 inside the fan housing 4.

As discussed above, the gap between the tapered air suction port sideend parts 33 d, 33 d, . . . of the vanes 33, 33, . . . and the innersurface of the recessed part 7 a of the bell mouth 7 of the fan housing4 is narrowly formed so that it is less than a prescribed value.Consequently, it is possible to suppress the generation of a reverseflow of air in the region close to the air suction port side end part 33d of the air outlet side edge part 33 b of each of the vanes 33, 33, . .. of the impeller 3 without providing the impeller 3 with an annularshroud opposing the annular bell mouth 7. Thereby, the flow speeddistribution becomes close to uniform, and the multi-vane centrifugalfan 1 can be operated with little noise.

The following enumerates the features of the multi-vane centrifugal fanaccording to the first embodiment.

Here, the recessed part 7 a having a prescribed depth is formed in thebell mouth 7 of the fan housing 4. Because the air suction port side endpart 33 d of each of the vanes 33, 33, . . . of the impeller 3corresponds to the cross sectional shape of the recessed part 7 a, thesealing performance is sufficiently high even without a shroud. Thereby,a reverse flow at the vicinity of the air suction port side end part 33d of each of the air outlet side edge parts 33 b, 33 b, . . . of thevanes 33, 33, . . . is suppressed while having the advantages of ashroudless structure (reduction in the number of parts, weight, and discfriction); consequently, the flow speed distribution over the entirearea of the space on the air outlet side of the vanes 33, 33, . . .becomes nearly uniform, and the relative velocity decreases. As aresult, the aerodynamic noise decreases.

In addition, because the gap is small between the air suction port sideend parts 33 d, 33 d, . . . of the vanes 33, 33, . . . and the innercircumferential surface of the recessed part 7 a of the bell mouth 7,there is little interference, and aerodynamic noise due to interferenceis also reduced.

In addition, as can be understood by comparing FIG. 4 with FIG. 9, ifthe shape corresponding to the cross sectional shape of the recessedpart 7 a of the bell mouth 7 and suited to sealing the vanes 33, 33, . .. is formed by, assuming the shape of the vane 133 whose conventionalvane width depicted in FIG. 9 is fixed at W1, cutting out part of thatair suction port side end part 133 d, then the weight of the vane 33decreases by just that portion, the load on the impeller drive motor 2decreases, and the breaking strength of each of the vanes 33, 33, . . .increases.

In addition, with the multi-vane centrifugal fan 1 according to thefirst embodiment, the vane width of each of the vanes 33, 33, . . . isconstituted so that the air outlet side edge part 33 b is smaller thanthe air inlet side edge part 33 a, and so that it decreases with apattern that varies with the arcuate shape having a prescribed curvaturefrom the air inlet side edge part 33 a to the air outlet side edge part33 b. Because it is so constituted, a more favorable sealing performancecan be achieved in the vicinity of the bell mouth 7.

In addition, because the vane width W1 of the air inlet side edge part33 a of each of the vanes 33, 33, . . . is made large while the vanewidth W2 of the air outlet side edge part 33 b is made small, the airsucked in from the air suction port 5 into the fan housing 4 can beblown out in the centrifugal direction more smoothly.

In addition, with the multi-vane centrifugal fan 1 of the firstembodiment, the annular member 32 for reinforcement is provided andarranged at the portion that is the air outlet side edge part 33 b,which is where the vane width of the vane 33 is smallest, and that isthe air suction port side end part 33 d. Because it is so constituted,if the air suction port 5 is disposed toward the upper side as depictedin FIG. 2, then the center of gravity of the impeller 3 shifts downwardand its rotational state is more stable compared with the conventionalmulti-vane centrifugal fan depicted in FIG. 7.

Second Embodiment

FIG. 5 depicts the constitution of the vane portion of the multi-vanecentrifugal fan according to the second embodiment of the invention ofthe present application.

Here, the shape of the notched part of the air suction port side endpart 33 d in the constitution of the abovementioned first embodiment ismodified to a shape wherein the vane width from the air inlet side edgepart 33 a to each of the air outlet side edge parts 33 b, 33 b, . . .decreases linearly from W1 to W2, as depicted in FIG. 5.

With such a shape as well, the clearance between the air suction portside end parts 33 d, 33 d, . . . of the vanes 33, 33, . . . and therecessed part 7 a of the bell mouth 7 can be reduced, sealingperformance can be ensured, and reverse flow can be suppressed; thereby,with this case as well, leakage flow in the vicinity of the bell mouth 7can be suppressed, and ventilation noise can be reduced.

Third Embodiment

FIG. 6 depicts the constitution of the vane portion of the multi-vanecentrifugal fan according to the third embodiment of the invention ofthe present application.

Here, the shape of the notched part of the air suction port side endpart 33 d in the constitution of the abovementioned first embodiment ismade to vary by decreasing in a curved shape (more specifically, anS-shaped curve) from the air inlet side edge part 33 a to each of theair outlet side edge parts 33 b, 33 b, . . . , as depicted in FIG. 6.

The notched part of the air suction port side end part 33 d can bemodified to a variety of curved shapes from the air inlet side edge part33 a to each of the air outlet side edge parts 33 b, 33 b, . . . ;however, if substantially S-shaped as mentioned above, then the entiretyof the air suction port side end part 33 d can particularly be made tocorrespond to the cross sectional shape of the recessed part 7 a of thebell mouth 7.

Thus, in this case, because the clearance to the recessed part 7 a ofthe bell mouth 7 can be reduced across the entirety of the air suctionport side end part 33 d, sealing performance can be further increased,and reverse flow can be effectively suppressed in the vicinity of theportion that is the air outlet side edge part 33 b and that is the airsuction port side end part 33 d. In addition, it also becomes moredifficult for leakage flow to be generated.

INDUSTRIAL FIELD OF APPLICATION

According to the multi-vane centrifugal fan of the present invention,operating noise can be effectively reduced without reducing fanefficiency.

1. A multi-vane centrifugal fan, comprising: a fan housing having an airsuction port forming plate forming an air suction port and a step part,and a bell mouth with a recessed part of a prescribed depth providedaround a circumference of the air suction port; and an impellerrotatably housed in the fan housing and including: a hub rotatablydriven around a shaft core, a plurality of vanes fixed to the hub andarranged with a prescribed spacing in a circumferential direction of thehub, and an annular member for reinforcement provided on a side of thevanes opposite the hub, the annular member being accommodated by thestep part, the recessed part having air suction port side end partspositioned on the side of the vanes opposite the hub and rotatablyinserted in the recessed part without having a shroud.
 2. The multi-vanecentrifugal fan as recited in claim 1, wherein each of the vanes has alongitudinal width in a shaft core direction that decreases with aprescribed variation pattern from an air inlet side to an air outletside.
 3. The multi-vane centrifugal fan as recited in claim 2, whereinthe prescribed variation pattern includes a pattern that changes a shapeof the air suction port side end part to a curved shape from the airinlet side to the air outlet side.
 4. The multi-vane centrifugal fan asrecited in claim 3, wherein the annular member is disposed at the airoutlet side of the vanes proximate the air suction port.
 5. Themulti-vane centrifugal fan as recited in claim 2, wherein the prescribedvariation pattern includes a pattern that changes a shape of the airsuction port side end part to an arcuate shape having a prescribedcurvature from the air inlet side to the air outlet side.
 6. Themulti-vane centrifugal fan as recited in claim 5, wherein the annularmember is disposed at the air outlet side of the vanes proximate the airsuction port.
 7. The multi-vane centrifugal fan as recited in claim 2,wherein the prescribed variation pattern includes a linear variationpattern in which a shape of the air suction port side end part linearlychanges from the air inlet side to the air outlet side.
 8. Themulti-vane centrifugal fan as recited in claim 7, wherein the annularmember is disposed at the air outlet side of the vanes proximate the airsuction port.
 9. The multi-vane centrifugal fan as recited in claim 2,wherein the annular member is disposed at the air outlet side of thevanes proximate the numerous vanes proximate the air suction port.
 10. Amulti-vane centrifugal fan, comprising: a fan housing having an airsuction port and a bell mouth with a recessed part of a prescribed depthprovided around a circumference of the air suction port, the fan housingforming a vortex chamber and an air blow out port passageway; and animpeller rotatably housed in the fan housing and including: a hubrotatably driven around a shaft core, a plurality of vanes fixed to thehub and arranged with a prescribed spacing in a circumferentialdirection of the hub, the prescribed spacing being fully open in a shaftcore direction and in a direction of a side of the vanes opposite thehub, and an annular member for reinforcement disposed on an outer sidein a radial direction of the vanes and integrated with a plurality ofend parts on the side of the vanes opposite the hub, the annular memberbeing aligned with a surface of the vortex chamber passageway or the airblow out port passageway, the recessed part having air suction port sideend parts positioned on the side of the vanes opposite the hub andinserted in the recessed part.